Hepatocellular carcinoma (HCC), a major form of liver cancer, is the second most common cause of cancer-related deaths worldwide. Its prognosis is poor, with a 5-year survival rate of less than 15%. The national prevalence and mortality due to cirrhosis and HCC in VA health care users have been increased by 2.5 to 3-fold during the last decade. The predicted increasing trend of HCC incidence and HCC-related deaths in the US veterans group remains alarming. Chronic hepatitis, alcoholic cirrhosis, fatty liver, and exposure to hepatotoxins are the major risk factors for HCC development. The risk of HCC increases strikingly in HCV carriers with diabetes and obesity. Thus, HCC is a major cause of deaths and veterans? health issue. A single FDA-approved medical therapy for HCC, sorafenib only extends survival by approximately 3 months. Curative surgical options include hepatic resection and liver transplantation. However, very few patients are surgical candidates due to a late diagnosis of HCC. One of the major obstacles preventing the development of effective therapeutic agents is due to the potential existence of tumor stem cells (TSCs) in HCC. Most tumors contain a small percentage (1% to 2%) of TSC population that are believed to be responsible for resistance to chemotherapy, relapse, and metastasis. We have shown that a TSC-related protein, doublecortin- like kinase 1 (DCLK1) is induced in hepatotoxicity-induced liver injury, chronic hepatitis, cirrhosis, and HCC whereas a normal liver lacks DCLK1 expression. The elevated DCLK1 level promotes hepatoma cell migration, cell cycle progression, and HCC-like tumor growth. Our central hypothesis is that activation of DCLK1-expressing cells contributes to the development of hepatic neoplasia and, ultimately, HCC. Targeting the DCLK1-expressing subpopulation and DCLK1 regulated signaling will reduce the burden of cancer-related deaths. The proposed investigations rely on the use of primary human hepatocytes derived from normal and patient donors. We will determine the mechanism(s) which promote DCLK1-expressing human hepatocytes to acquire tumor characteristics. We will use cell culture and a unique mouse model with humanized/chimeric liver to test the hypothesis. We will also develop HCC patients-derived tumor xenografts to evaluate the impacts of targeting DCLK1 in HCC. Taken together, these studies will increase our understanding of the mechanism(s) that regulate hepatic neoplasia and will potentially validate DCLK1 as a new therapeutic target in HCC. These studies, if successful, will have a major impact on the field of cancer and veterans? health because DCLK1 also contributes to the tumor growth in pancreas, intestine, and colon. !